The invention relates generally to steam cooking and more particularly to methods for steam-heating nuts with forced convection at temperatures below 100° C. (212° F.).
Nuts, such as almonds, are often pasteurized by immersion in hot water or an air-steam environment. Steam pasteurizers conventionally use the heat of condensation to heat the outer surfaces of nuts to temperatures high enough to deactivate enough micro-organisms to meet acceptable pasteurization levels. The nuts enter the steam pasteurizer at a temperature below the temperature of the steam. The steam condenses on the outer surface of the nuts and raises their temperature. But the condensation can wrinkle and loosen the outer skins of the nuts. In the case of almonds and other nuts to be sold in their skins, the nuts' uptake of water should be limited. One approach to limiting condensation in almonds is described in International Patent Publication No. WO 2013/171336. That document teaches pre-heating low-moisture foods to a temperature above or slightly below the condensation temperature of the water vapor in the heating chamber to limit condensation. Another approach, described in U.S. Patent Application Publication No. 2013/0040030, steams nuts at a pressure below atmospheric to limit water uptake. But pre-heating requires an additional heater, and a vacuum system requires batch and not continuous handling.